Field of the Invention
The present invention relates to a coil component and its manufacturing method and, more particularly, to a coil component using a drum-shaped core and its manufacturing method. The present invention further relates to a circuit substrate and, more particularly, to a circuit substrate provided with the coil component using the drum-shaped core.
Description of Related Art
In recent years, electronic components used in an information terminal device such as a smartphone is strongly required to be reduced in size and height. Under such circumstances, a large number of surface mount coil components such as a pulse transformer using a drum-shaped core, not a toroidal-shaped core are used. For example, Japanese Patent Application Laid-Open No. 2014-199906 discloses a surface mount pulse transformer using the drum-shaped core.
In the drum-shaped core of the pulse transformer described in Japanese Patent Application Laid-Open No. 2014-199906, a mounting surface of a flange portion of the core has a concavo-convex shape, and a wire end portion is connected to a convex portion (see FIG. 2 of Japanese Patent Application Laid-Open No. 2014-199906). Each flange portion has four convex portions, and side surfaces of the four convex portions positioned at both ends of the core coincide with side surfaces of the flange portions.
However, when a plurality of pulse transformers described in Japanese Patent Application Laid-Open No. 2014-199906 are mounted on a circuit substrate in proximity, a distance between the adjacent pulse transformers is too small, which may deteriorate reliability. In particular, when a part of the terminal electrode is formed also on the side surface of each convex portion, a solder fillet is formed on the side surface of each convex portion, with the result that the above problem becomes more prominent.
The above problem is not a problem that occurs only in the pulse transformer, but a problem occurs commonly in coil components using the drum-shaped core.